Common Winter Cress or Yellow Rocket, Barbarea vulgaris
Brassicaceae or Mustard Family

Alien weed, about 2 ft tall, with green heads from which bright yellow flowers protrude.  Flowers have four petals.  Lowest leaves have one large lobe at the end and 2-8 smaller lobes.  Upper leaves are toothed.  Weedy plant that grows along the bikeway and Wildwood Drive.

A similar weed, early winter cress (B. verna) also occurs in southwest Virginia and could be expected in the Park.  It has 8-20 lobes on its lowest leaves, and lobed upper leaves.